For a woman's breasts, pregnancy marks the role of a lifetime. As soon as they get the hormonal signal that this month's egg has been fertilized and implanted in the uterus, those amazing mammary glands start cooking. Almost before you know it, they grow by leaps, bounds, and cup sizes on the outside, while furiously developing a milk production network on the inside. After all, pregnancy -- or its culmination, a tiny mouth to feed -- is what women's breasts have been waiting for since puberty. Here's an insider's guide to what's happening and what you can do about the aches, pains, drips, and droops that can affect pregnant breasts from conception to mission accomplished.